How to DIY a SuzyQ Cable
How a SuzyQ Cable Actually Works
Chromebooks with a Titan C / Cr50 / Ti50 security chip monitor the USB Type-C Configuration Channel (CC) lines for a specific resistor combination:
- CC1 (pin A5): Pulled to VBUS via a 22 kΩ resistor.
- CC2 (pin B5): Pulled to VBUS via a 56 kΩ resistor.
When the Chromebook detects these exact pull-up values upon insertion, it enters Debug Accessory Mode. The internal multiplexer redirects the security chip's USB lines to the USB-C Sideband Use (SBU) pins:
- SBU1 (pin A8) becomes USB D+.
- SBU2 (pin B8) becomes USB D-.
Once connected to your PC, the Chromebook's security chip enumerates natively on your host system as a Google USB composite device (VID:PID 18d1:5014), exposing serial consoles for the AP and EC, as well as the CCD interface used by gsctool and flashrom.
How to Build a DIY SuzyQ (No Microcontroller Required)
To build one, you only need:
- A male USB-C breakout board with access to individual pins (all 24 pins exposed, or at least VBUS, GND, CC1, CC2, SBU1, and SBU2).
- Two resistors: 1x 22 kΩ (1% tolerance) and 1x 56 kΩ (1% tolerance).
- A sacrificial USB 2.0 cable (USB-A or USB-C on the PC side).
Wiring Diagram
| USB-C Male Plug (to Chromebook) | Connection / Resistor | Host USB Cable (to PC) |
|---|---|---|
| VBUS (A4, A9, B4, B9 bridged) | Direct wire | 5V (Red) |
| GND (A1, A12, B1, B12 bridged) | Direct wire | GND (Black) |
| CC1 (A5) | 22 kΩ resistor to VBUS | (No connection to host) |
| CC2 (B5) | 56 kΩ resistor to VBUS | (No connection to host) |
| SBU1 (A8) | Direct wire | D+ (White) |
| SBU2 (B8) | Direct wire | D- (Green) |
Crucial build note: You must use a male USB-C plug breakout inserted directly into the Chromebook. Standard USB-C to USB-C or extension cables do not wire both CC lines end-to-end (only one CC wire exists in standard Type-C cables, with the other line used for VCONN). Splicing an existing USB-C cable will fail.